This invention relates to gas well production and more particularly to a check valve to prevent back flow of gas to a producing gas well.
1. Field of the Invention
It is difficult to obtain accurate gas measurement on low volume gas wells situated in old fields on account of pipeline pressure changes as result of fluid in the line down stream from a meter. When these pressure changes occur the gas reverse flow through the meter toward the producing well registers a very wide differential line above and below zero on the meter chart. This is usually interpreted as gas produced and the pipeline company pays for gas they never receive.
In a gas gathering system, the gas lines from producing gas wells are connected together and the gas conveyed by a single line to a processing plant which prepares the gas, such a by removing water therefrom, and pumping it to consumers.
Water is sometimes produced with or collects by condensation in the gas line and where the gas line passes over a rise in the earth's surfaces or under a highway right-of-way for example, water collects on the down hill or gas production side in the gas line and gas pressure must be increased by the producing well or wells until sufficient pressure is generated to force the water or other liquid over the rise in the gas line or under the highway right-of-way.
Some gas wells have less formation pressure than others and this necessary gas pressure increase in the gas line sometimes results in a back flow of gas into a relatively low formation pressure gas producing well and the above described erroneous reading of gas production from a low pressure gas well and paying royalty a second time on gas previously produced. When the obstruction or water is moved by gas pressure increase through the collection line all wells resume normal gas production.
This invention provides an inline check valve for a low pressure gas producing well flow line which permits gas flow from the gas well to the collection line or system but prevents reverse flow toward the gas well.
2. Description of the Prior Art
Inline liquid and gas back flow check valves are well known in the oil and gas industry. However, the structural requirements and physical dimensions of all commercially available check valves within my knowledge are incapable of being easily interposed between existing bolt flanges in a parted pipeline for preventing a reverse flow of relatively low pressure gas.
The most pertinent patent is believed to be U.S. Pat. No. 2,602,631, issued to Eickmeyer, Jul. 8, 1952, for Check Valve. This patent discloses a centrally divided flange connected valve body having opposing converging ends interposed between respective ends in a parted pipeline for preventing back flow of water from irrigation lines into the water well.
The valve body contains a valve seat and a piston-like valve moved upstream toward and away from the seat by a spring surrounding a valve guiding stem projecting downstream.
U.S. Pat. No. 4,782,855, issued Nov. 8, 1988, to Scaramucci, for Check Valve Seat and Cage Retainer, and U.S. Pat. No. 4,485,844, issued Dec. 4, 1984, to Vander Kaay et al, for Back Pressure Valve Inducer, are believed to represent the state-of-the-art.
The Scaramucci patent discloses a ring-like cage member supporting a disc or clapper moved toward and away from an axial seat in the cage by gravity and fluid flow is interposed in a fluid line.
The Vander Kaay et al patent discloses a annular valve seat interposed in a fluid line forming a port. A valve member supported from the upstream side of the valve seat is spring forced toward the valve seat.
This invention is believed distinctive over these and other patents of the prior art by providing a flat disc having a central bore forming a valve seat and is interposed between flanges of adjacent joints in a pipeline.
A valve body containing a spring urged valve moveable toward and away from the valve seat is secured to the disc downstream face within the bore of the downstream pipe joint surrounding the valve body, the valve body being provided with a plurality of fluid outlet ports.